Consolidation pass: HR-only access, effective-dated mutations, data integrity guards, test suite

Reworks the app from a two-role (hr_admin/manager) model to a single
HR-only role gated by profiles.is_active, fixes transfer/promote/karenz/
reorg RPCs to actually defer future-dated changes via a new
pending_org_changes table instead of writing them immediately (applied
by a daily Vercel Cron route), makes reorg undo append-only instead of
deleting history, adds Karenz-return and history-date integrity guards,
deprecates the salary column, and adds explicit schema grants + perf
indexes needed to run against a fresh (non-hosted) Postgres instance.

Adds vitest unit + integration test suites (the latter against a real
local Supabase instance) covering all of the above, plus lint/typecheck/
build wiring (`npm run check`).

tests/unit/format.test.ts

@@ -0,0 +1,78 @@
+import { describe, expect, it } from "vitest";
+import { daysBetween, fmtAge, fmtDate, initials, tenure } from "@/lib/format";
+
+describe("fmtDate", () => {
+  it("formats an ISO date string in de-AT order", () => {
+    expect(fmtDate("2026-03-05")).toBe("05.03.2026");
+  });
+
+  it("returns an em dash for null/undefined/empty input", () => {
+    expect(fmtDate(null)).toBe("–");
+    expect(fmtDate(undefined)).toBe("–");
+    expect(fmtDate("")).toBe("–");
+  });
+
+  it("returns an em dash for an invalid date string", () => {
+    expect(fmtDate("not-a-date")).toBe("–");
+  });
+});
+
+describe("initials", () => {
+  it("uppercases the first letter of each name", () => {
+    expect(initials("maria", "gruber")).toBe("MG");
+  });
+
+  it("trims surrounding whitespace before taking the first letter", () => {
+    expect(initials("  Anna", "Huber  ")).toBe("AH");
+  });
+});
+
+describe("fmtAge", () => {
+  it("computes age correctly when the birthday has already passed this year", () => {
+    const today = new Date();
+    const birthDate = new Date(today.getFullYear() - 30, 0, 1); // Jan 1, definitely passed
+    expect(fmtAge(birthDate)).toBe(30);
+  });
+
+  it("subtracts one year when the birthday has not yet occurred this year", () => {
+    const today = new Date();
+    const future = new Date(today.getFullYear() - 30, 11, 31); // Dec 31, likely not yet passed
+    if (today.getMonth() === 11 && today.getDate() === 31) return; // skip on the one day this'd be flaky
+    expect(fmtAge(future)).toBe(29);
+  });
+});
+
+describe("tenure", () => {
+  it("formats whole years and months since entry", () => {
+    const start = new Date(2020, 0, 15);
+    const end = new Date(2023, 2, 15); // exactly 3 years, 2 months later
+    expect(tenure(start, end)).toBe("3 Jahre, 2 Monate");
+  });
+
+  it("uses singular Jahr/Monat for exactly 1", () => {
+    const start = new Date(2020, 0, 1);
+    const end = new Date(2021, 1, 1); // 1 year, 1 month
+    expect(tenure(start, end)).toBe("1 Jahr, 1 Monat");
+  });
+
+  it("falls back to 'unter 1 Monat' for less than a month", () => {
+    const start = new Date(2024, 0, 1);
+    const end = new Date(2024, 0, 15);
+    expect(tenure(start, end)).toBe("unter 1 Monat");
+  });
+
+  it("defaults the end date to today when no end date is given", () => {
+    const start = new Date();
+    expect(tenure(start)).toBe("unter 1 Monat");
+  });
+});
+
+describe("daysBetween", () => {
+  it("computes whole days between two dates", () => {
+    expect(daysBetween("2026-01-01", "2026-01-11")).toBe(10);
+  });
+
+  it("returns a negative number when the second date precedes the first", () => {
+    expect(daysBetween("2026-01-11", "2026-01-01")).toBe(-10);
+  });
+});